unicode type forgotten in api_client.mustache

Author: DariusMR

modules/swagger-codegen/src/main/resources/python/api_client.mustache

@@ -189,7 +189,7 @@ class ApiClient(object):
         """
         if isinstance(obj, type(None)):
             return None
-        elif isinstance(obj, (str, int, float, bool, tuple)):
+        elif isinstance(obj, (str, int, float, bool, tuple, unicode)):
             return obj
         elif isinstance(obj, list):
             return [self.sanitize_for_serialization(sub_obj)